1. Field of the Invention
This invention relates to the editing of recorded material such as audio and/or video material.
2. Description of the Prior Art
As an example, video edit controllers are used to edit a number of xe2x80x9crawxe2x80x9d source video sequences into a final programme or part of a programme. For example, a short news story may contain brief excerpts of a number of different video sequences, possibly including newly captured and older, archived sequences, in order to illustrate different aspects of the news story. A relevant portion or xe2x80x9cclipxe2x80x9d of each sequence needs to be selected, and the selected portions linked together to form the composite output sequence.
Recently, computer-based non-linear edit controllers have become available. These allow a user to view the source sequences on a computer screen and to select an xe2x80x9cin-pointxe2x80x9d and an xe2x80x9cout-pointxe2x80x9d for each required sequence or clip using the computer keyboard or a cursor control device such as a mouse, joystick or trackerball. The selected clips can then be ordered to form the desired output sequence.
In such a computer-based system, it has been proposed to load the required source sequences from the usual tape medium onto a random access storage device such as a hard disk or magneto-optical disk associated with the computer before editing takes place. This allows the user to view different sequences in very quick succession, without the delays normally associated with tape media such as the need to change tapes or to shuttle to a different part of the same tape.
This invention provides editing apparatus for editing source video and/or audio material stored on a storage medium to generate an edited material sequence of clips from the source material, the apparatus comprising:
means for defining source files on the storage medium containing data representing the source material to be edited; and
means for defining an output file on the storage medium for each edited material sequence, each output file comprising addressing information defining a sequence of storage locations on the storage medium of data within the source files representing the one or more clips of source material forming that edited material sequence.
The invention recognises that in an editing system based on a random access storage medium such as a disk drive, it has previously been a complex and processor-intensive operation to replay an edited sequence containing clips from multiple source material files. In particular, in such a previous system, each source file has to be opened in turn (and generally in advance of the time when it is needed), the clip of material has to read from that source file, and then the source file has to be closed. This type of sequential operation has been referred to as xe2x80x9ctime linexe2x80x9d based operation, and works well in a normal speed, forward direction replay. However, it does not lend itself to more unusual replay operations, such as reverse, jog or shuttle replay, nor to replay starting at an arbitrary point within the sequence.
The invention provides a new way of organising the stored data for an edited output sequence, by creating what will be referred to as an output or xe2x80x9cvirtualxe2x80x9d file representing the output sequence. This is a file on the storage device with no dedicated material data, but simply having a sequence of pointers to sections of stored data relating to xe2x80x9crealxe2x80x9d (or source) files.
Thus, in order to replay the virtual file, the sequence of pointers is followed through in order to access the required data from sections of the disk. In at least embodiments of the invention, this uses the same techniques that are employed to cope with disk fragmentation for real files. However, in contrast to the xe2x80x9ctime-linexe2x80x9d operation mentioned above, the virtual file can be replayed in either direction and from arbitrary starting points within the file.
This invention also provides a data storage medium for storing source video and/or audio material, edited to form an edited material sequence of clips from the source material, the data storage medium storing:
source files containing data representing the source material to be edited; and
an output file for each edited material sequence, each output file comprising addressing information defining a sequence of storage locations on the storage medium of data within the source files representing the one or more clips of source material forming that edited material sequence.